1. Field of the Invention
The present invention relates to a digital automatic power interruption and re-supply relay installed at a low voltage spot or a high voltage spot on a power transmit and supply line of high and low voltage or special high voltage and high (low) voltage, for performing detection and comparing operation to inform a state of an accident with voice and numerals and automatically operating a connected relay to interrupt power when there occur abnormal changes such as interruption of electric power, open-phase, anomalous voltage, unbalanced voltage, negative-phase, overcurrent, and electric leakage and, after compensating for the accident, for automatically re-supplying the power.
2. Description of Related Art
Conventionally, the electric power line is protected from interruption of electric power, undervoltage, overvoltage, or an open-phase occurring at the secondary coil of the electric power line, using a 3E relay, overvoltage relay, undervoltage relay, and phase open relay (POR) employing a dedicated potential transformer (PT). However, such relays do not operate in case of the anomalous voltage, unbalanced voltage, and open-phase at a primary coil and do not re-supply the power, so there is a problem of failing in supplying the power with good quality. To solve the problem, we filed Korean Pat. Appln. No. 97-7929 for an analog emergency protective device for the electric power line on Mar. 5, 1997, and the Korean Pat. Appln. No. 98-6196 for the same is filed as a national priority application on Feb. 28, 1998. The application is the prior art over the present invention.
The emergency protective device for the electric power line according to the prior art employs an analog mode and comprises: first to third detection converters for detecting currents flowing in three phases of the electric power line into DC ripples; a comparator for differentially amplifying the DC ripples and comparing the phases to provide a result in the form of a positive polar pulse or a negative polar pulse; a drive unit activated in response to the positive or negative polar pulse output, for generating a state output "1" or "0"; and a controller implemented with a central processing unit (CPU) that is a microprocessor for selectively outputting alarm, interruption, and re-supply instructions in response to the state output from the drive unit. Recently, the digital mode has been rapidly developed, so the conventional analog control parts are required to be digitalized in order to swiftly obtain accurate control results desired.